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The evolution of cooperation has been a focus of interest for evolutionary biologists for over a hundred years (Darwin 1859; Kropotkin 1908; Williams 1966). While all forms of cooperation challenge the centrality of competition in the process of evolution, cooperative and eusocial breeding systems, where offspring produced by a small number of breeding individuals are reared by nonbreeding helpers or workers, raise some of the most fundamental questions about the level at which selection operates the measurement of....
No abstract is provided for this article.
No abstract is provided for this article.
In cooperative societies, group members are expected to be punished for being lazy and so behaviours that exaggerate an individual's contribution to cooperation may be favoured by selection. In cooperative meerkats, Suricata suricatta, helpers vary in their level of care and, within breeding attempts, helpers can be categorized as ‘generous’ or ‘lazy’. Lazy helpers were more likely to carry food to pups and then eat it themselves and lazy males received more aggression, supporting the idea that ‘false feeding’ could be an adaptive tactic used to exaggerate individual contributions to care. However, our results are also consistent with the more parsimonious idea that ‘false feeding’ occurs when individuals decide not to deliver food items after assessing the needs of pups relative to their own. Group members were not obviously deceived by ‘false feeders’ nor was ‘false feeding’ associated with any obvious benefit. In general, the frequency of ‘false feeding’ increased when the net benefits of feeding pups were likely to be low. The frequency of ‘false feeding’ increased with rising food item value and with decreasing pup dependency on food provided by helpers. Female helpers (which feed pups more than male helpers and preferentially feed female pups) ‘false fed’ less than male helpers and ‘false fed’ male pups more than female pups. We suggest that there is little unequivocal evidence of deception by helpers over contributions to care in cooperative vertebrates and that ‘false feeding’ may occur where helpers adjust their decisions immediately before feeding young or where they are subject to conflicting motivations.
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Since 1994, the combination of mefloquine and artesunate is the standard treatment for uncomplicated Plasmodium falciparum malaria in the population of displaced persons on the Western border of Thailand. As a result, the fall of mefloquine efficacy was stopped and the incidence of falciparum malaria reduced. This is attributed to the effects of the artemisinin derivatives on transmissibility. Similar trends were observed in Vietnam where artemisinin is widely used. Combination therapies that include an artemisinin derivative could have a major role in the control of malaria and the spread of drug resistance.
Evidence of an association between cooperative breeding systems and average coefficients of relatedness between group members in vertebrates have led to increased interest in the social and ecological factors affecting average kinship within groups. Previous studies have suggested that polygynous mating systems and high degrees of male reproductive skew increase average relatedness because they increase the proportion of offspring born in each group that are paternal siblings. Although this may be the case in semelparous organisms, in many multiparous polygynous animals, intense competition between males shortens the breeding tenure of males and leads to their frequent replacement by competitors which reduces paternal relatedness and average kinship between members of multigenerational groups. Here, we explore the interaction between male reproductive skew and the frequency of turnover in breeding males and its effects on within-group relatedness. Our theoretical model shows that increases in rates of dominance turnover in polygynous systems can offset the positive effect of male skew on relatedness between group members within seasons, showing that polygynous mating systems will not necessarily lead to significant increases in average relatedness, especially in species where there is extensive overlap between generations among group members.
Individuals vary in their potential to acquire and transmit infections, but this fact is currently underexploited in disease control strategies. We trialled a trait-based vaccination strategy to reduce tuberculosis in free-living meerkats by targeting high-contact meerkats (socially dominant individuals) in one study arm, and high-susceptibility individuals (young subordinates) in a second arm. We monitored infection within vaccinated groups over two years comparing the results with untreated control groups. Being a member of a high-contact group had a protective effect on individuals' survival times (Hazard Ratio = 0.5, 95% Confidence Interval, CI: 0.29-0.88, p = 0.02) compared to control groups. Over the study, odds of testing positive for tuberculosis increased more than five-fold in control groups (Odds Ratio = 5.40, 95% CI = 0.94-30.98, p = 0.058); however, no increases were observed in either of the treatment arms. Targeted disease control approaches, such as the one described in this study, allow for reduced numbers of interventions. Here, trait-based vaccination was associated with reduced infection rates and thus has the potential to offer more efficient alternatives to traditional mass-vaccination policies. Such improvements in efficiency warrant further study and could make infectious disease control more practically achievable in both animal (particularly wildlife) and human populations.
Praziquantel undergoes extensive first-pass hepatic biotransformation, but there is little information on its disposition or toxicity when administered to patients with liver disease. To define the influence of liver disease on the pharmacokinetics of praziquantel, we administered it orally to 30 patients with proven Schistosoma japonicum infection whose liver disease was carefully assessed as being severe, moderate, or absent. Both the peak plasma concentration of praziquantel and the bioavailability (measured as the area under the plasma concentration time curve) were significantly greater in the two groups of patients with liver disease (P < .005), as were the concentrations of the two identified metabolites of praziquantel. Mild side effects were associated with high peak concentrations of praziquantel, but a syndrome of severe abdominal pain followed by bloody diarrhea was not. Our results indicate that the side effects and bioavailability of praziquantel are increased in the presence of liver disease.
